The research proposed in the present application is an extension of the original application entitled, "A Study of the Factors Controlling Cellular Proliferation in Mammalian Cells". It is intended to continue these studies both in the original system (the isoproterenol-stimulated salivary gland) and in contact-inhibited WI-38 human diploid fibroblasts stimulated to proliferate by a change of medium. Specifically, it is now proposed to study the synthesis of nuclear acidic proteins in cells stimulated to proliferate and to ascertain their role in the control of cellular proliferation in mammalian cells.